Uranium is a chemical element in the periodic table that has the symbol U and atomic number 92. A heavy, silvery-white, toxic, metallic, and naturally-radioactive element, uranium belongs to the actinide series and its isotope 235U is used as the fuel for nuclear reactors and nuclear weapons. Uranium is commonly found in very small amounts in rocks, soil, water, plants, and animals (including humans).
Notable characteristics
When refined, uranium is a silvery white, weakly radioactive...

A pivoted catch designed to fall into a notch on a ratchet wheel so as to allow movement in only one direction (e.g. on a windlass or in a clock mechanism), or alternatively to move the wheel in one direction.